Telecommunication carriers are required by government regulations to provide emergency calling services to their customers. In the United States and Canada, 911 is the official emergency phone number that callers can dial in order to reach dispatch personnel at a public safety answering point (PSAP). When a caller dials 911 from a telephone, the call is routed by a carrier to receiving equipment at a PSAP facility. A dispatcher at the facility answers the call and assists the caller with their emergency.
Often times, dispatchers must dispatch first responder personnel to the scene of an emergency to render assistance to callers. In the past, dispatchers had to ask a caller for his location. Over time, most telecommunication carriers developed the capability to automatically determine the location of caller who dialed 911 via a landline. For instance, 911 callers on a landline can be located based on their phone number. In the case of broadband 911 voice calls, callers can be located based on the identity of their broadband equipment.
During the course of a 911 call made from a mobile phone, a PSAP or other emergency services provider may request the carrier determine the approximate location of a mobile 911 caller. Once the carrier determines an approximate location of a mobile caller, this information may be relayed to the PSAP. This approximate location may also be used to determine which PSAP should receive the 911 call.